Progressive metal stamping in which a metal strip or the like is guided along a predetermined path in cadence with the operation of a reciprocating stamping press, is well known in the art. In a conventional technique, one or more flat strips of metal stock are fed into a specially manufactured tool called a “die set” that is located within, and actuated by a stamping press. Metal stamping die sets typically comprise two associated halves, which together are referred to as a “punch and die.” A conventional punch and die set has an upper shoe and a lower shoe to which metal forming, cutting, coining, bending, drawing, blanking, notching, embossing, forming, piercing, and punching tools may be mounted. Upon each reciprocating movement or “stroke” of the stamping press, the metal strip is lifted and then advanced by one step through the die set. The tools that are located within the die set move toward and away from the surface of the metal strip during each full cycle of the press. Through the pressure and motion of the die set within the stamping press, the various tools cut out and/or form the metal strip into parts or components of the required size and shape. Metal stamping dies are used to manufacture parts ranging from very small and/or sophisticated components for the electronics industry, to large shapes such as portions of an automotive body. Stamping presses are available in a wide variety of sizes and capabilities, depending upon the size and complexity of the required parts. Stamping presses can produce small parts at very high rates, and may operate at over 3,000 vertical strokes per minute.
The movable part of the stamping press, that is often attached to the upper shoe of the die set, is known as a “ram.” The ram moves the upper portion of the die set up and down relative to the lower half of the die set, which is stationary and mounted upon a heavy bolster plate defining a fixed bed. For dependable, correct operation the relative positions, dimensions, and alignment of the two halves of the die set are critical. A lack of sufficient clearance, or unintended contact between portions of the upper and lower die sets can wear or destroy the tools. Thus guidance of the ram during each stroke of the stamping press is a critical factor in accurate and precise die set operation. Conventionally, stamping press rams have utilized four or eight point alignment systems employing either hardened steel plates (gibs) or roller bearing and race elements that are mounted to the corners of the ram, and aligned with the stamping press frame and bed. Such stamping press guidance structures must be heavy and durable if they are to survive a large number of operations. This requirement can make it all the more difficult to ensure accurate and repeatable motion in very heavy driving arrangements needed for durability and longevity. While many stamping presses can operate with ram alignment accuracies in the thousandths of an inch, the tools mounted in their respective die sets must maintain tolerances measured in ten-thousandths, or even millionths of an inch.
As a consequence, there has been a long felt need for a ram guidance system suitable for a wide variety of stamping presses, that provides for greater ram alignment accuracy, approaching the accuracy of the die sets mounted in them.